Patent Document 1 discusses an example of a multistage compressor having a low-stage compression mechanism and a high-stage compression mechanism that are provided within a sealed housing and are driven by an electric motor. In this multistage compressor, the electric motor is disposed in a substantially central section inside the sealed housing, and a low-stage rotary compression mechanism is disposed below the electric motor, whereas a high-stage scroll compression mechanism is disposed above the electric motor. Moreover, the low-stage rotary compression mechanism and the high-stage scroll compression mechanism are driven by the electric motor via a rotary shaft.
The aforementioned multistage compressor is configured to take low-temperature refrigerant gas from a refrigeration cycle side into the low-stage rotary compression mechanism through an intake pipe, compress the refrigerant gas to intermediate pressure, discharge the intermediate-pressure refrigerant gas temporarily into the sealed housing, take the intermediate-pressure refrigerant gas into the high-stage scroll compression mechanism so as to compress the refrigerant gas to a high-temperature high-pressure state in two stages, and then discharge the refrigerant gas to the outside through a discharge pipe; hence, the inside of the sealed housing is in an intermediate-pressure refrigerant-gas atmosphere.
Patent Document 1:
Japanese Unexamined Patent Application, Publication No. Hei 5-87074